Overload protective device



Jan. 24, 1950 H. E. SCHLEICHER 0 OVERLOAD PROTECTIVE DEVICE 2 Shets-Sheet 1 Original Filed Nov. .26, 1943 Original Filed NOV. 26, 1945 2 Sheets-Sheet 2 Jan. 24, 1950 H. E.ISCHLEICHER 2,495,503

OVERLOAD PROTECTIVE DEVICE Patented Jan. 24, 1950 2,495,608 OVERLOADPR'OTECTIVE DEVICE HaroldxE; Schleicher,- West Hartford, Conn assignor to-The Arrow-Hart & HegemanElectric Gompany, Hartford, Conn., av corporation'of' Connecticut Originalapplication November." 26, 1943;:Scrial- Divided and this. application Marci r23; 1945, Serial N:-584,301

g 14 Claims.

p This invention relates to electricswitches, particularlyswitches used as overload relays to con: trol=-the opcrationzof other switches for heavier duty such as electro-magnetically actuated switches for'controlling powerline-circuits v Modern-battle oonditions require electrical control apparatus to withstandhighrimpact shocks. Theserequirementsv have-been met by. newly invented balanced types of electro-magnetically. operatedswitches suchrasdisclosed in my co-pendingapplication Serial No.. 511,855entitledlRotary magnetic switchg filed November 26, 1943, of which this application is: a division. .Such Switches will rcmainclosed even when subjected toenormous shocks and vibrations.

Overload protective devices usedv in connection with .thesenewly invented. electro-magnetic switches necessarily .must perform under the sameconditions' as those switches. Hence, the protective devices, like the main. switch, must be constructed to dominate those conditions;

I Ehus'it is: an object of! the invention to provide overload protectivedevices. for use with, and under the sameconditions as, balanced shockproof electro-magnetic switches of the afore' mentioned type.

Another object is to provide; overload protec tive devices embodyin'gshockprooi features and in which the. principles of dynamic balance are observed and-incorporated, in order (I); to preserve the eflectiveness. of' the incorporation. of those same principles in associated devices and (2) toinsure (whether or not the associated devices are-constructedoh and embody bal'anced and shockproof principles) accurate operation of the; protective d'evi'ces and. their operation only at the; time: and under the desired predetermined conditions. v p Other objects and advantages will becomeapparent as the invention is. described inconnection with the accompanying drawings.

the drawings g 1 is a plan viewloo ki'ng intocne face of a switch section err-1bcdyi'rig the invention;

2 is a view similar to Fig. .11 but with the heater coils and fixedcontrol I contacts removed; Fig. 3 is a plan .viewlooking inthe opposite face of the deviceofFig. 1;

i Fig. 4 is a .viewsimilar toFig. 3, withsorneof the tripping mechanism and itsresetting means mq dy Fig.-;5 is asectionview taken alongl-ine 5P5 a. c c y Fig. -6 is a sectionview'teken transversely along V '2' Fig. 7' is a section view" taken along ;1ine1T-T ofFig;1; I

Fig; 8 is a detail viewpshowing; in" elevation tripping mechanism that was'removed" fromFi'g; i; and

Fig; 9 is an explodediperspective view of the tripping mechanism of'Fig. 8".

v The present invention in" overload protective devices particularly useful in military installatlonsi where sudden. severe shocks and" vibrations are likely' to occur at anytime. The invent-ion is furthermore, particularly" suited for use with l'ialanced switching" devices such as the rotary electromagnetic switch of my co-pending application Serial No; 511,855; and-has been designed and formed in its various parts tofit' alongside and'to be a unitor section of the complete structure illustrated and described in said co-pending application. However; the present'invention;v in both structure and principle; is capable of use in many other situations and-fields; withlittle orno change in form.

Whenconditions of use require a balanced switching device of the type, for example,. as. in my application SerialNo. 511 3855} equally importtant in the protective end of the device is-zthe need to prevent actuation, whemshocks-"occur, for unless the overload or protectivewdevicesbe shock-proof, they may operaterunder shock con:- ditions to trip the breaker open in: spite: of 'al l precautions taken in making the breaker-itself shock-proof.

Generally, such devices as are herein contem plated are used in three wire power'line systems and must be capable of breaking; the circuitbn overload occurring in either; of the: two outside lines; the neutral not beingidirectly and separately protected.

The overload protectivedevices themselves are mounted upon a molded: insulation mountingdisc 1'30 which is suitably and symmetrically'irecessed at various pointsand placesonzieachasider of a vertical axis of symmetry forxthe-individualzelse ments which. make, up the; dual. protective, devices; On one side: oizthe tmountingmdisc l ma-are mounted the heater coils; and "bimetallic strips (see Figs. 1- and 2) ;on the: other side tsee Eigs. 3' and 4') ismounted thebalanced. tripping mecha nism which controls a rotary switch connectible in theicircuit tobe proteeted forexample, electro-magnetic circuit so as to accomplish .deenergization of the .rnagnet and -resultant circuit opening movement of a magnetic switch. .The

tripping. mechanismhis a. removable ,nnit (see, Fig.

ii wherein it is removed) which can be. tripped 3 by the action of bimetallic strips I44 and I45 responsive to heat developed on overload in resistance wire coils I32, I34 carrying main line current and placed next to the bimetallic strips.

Outside connections to the heater coils are made through identical stamped sheet metal terminal members I36, I 38 mounted in diametrically opposite radially directed recesses at the periphery of the mounting disc I30 having their terminal portions, such as I 36a, extending beyond. To accommodate the heater coils and bimetal members, oblique channels I 33, I35 convergent from the inner ends of the terminal members I 36, I38 are formed in the mounting disc. At the inner ends of these channels, L-shaped stamped sheet metal connectors I40, I42 form a mounting to which one end of the heater coils is secured, their opposite ends being screwed to the terminals I36, I38, whereby the coils are positioned in the upper part of the channels. Electric connection of the heaters I32, I34, for example, to the outside lines of a three wire system, may be made by terminal bolts H8 and IIS respectively.

Located beneath, and substantially parallel to the axis of the heaters I 32, I34 are bimetal strips I44, I 48 mounted at one end on small brackets I43, I45. The brackets are each secured at one end to the mounting disc I30 by through bolts I41.

To adjust the bimetal strips one end of the bimetal supporting brackets I43 receives a screw bolt I50, which is bored through and internally threaded to receive a calibration compensating screw I52 that engages one end of a lever I54 pivotally mounted near one end in the disc I30.

The other end of the lever engages the under surface of the bimetal so that on turning the adjustment bolt and screw the lever is rocked to vary the position of the bimetal with resultant variation in the amount of flexure thereof that will cause the latch I88 to trip free of the latch disc 200. Suitable locking means, as shown, are provided to maintain the position of adjustment of the screw I52 and bolt I50.

In order that the bimetal strips may act on the tripping mechanism on the opposite side of the mounting disc I30, the disc is pierced with openings I30a (Figs. 4 and 2) beneath the free ends of the bimetal strips at the end of the channels I 33, I 35, where the connectors I40, I42 are. As the bimetal strips flex on overload, their ends (one or both) enter the openings I30a to engage buttons I 95 on the trigger member of the tripping mechanism now to be described.

The tripping mechanism is carried by a frame that may be stamped from sheet metal in the form best indicated in Fig. 9. The central portion of this frame I80 is in the form of a parallelogram, from the opposite corners of which there are extensions I82, I84. The extension I82 has lateral arms or lugs I86 bent up at right angles thereto, between which is located the dynamically and statically balanced pivoted trigger member I88 which is preferably formed from molded insulating material into hexagonal prismatic form. In order to resiliently maintain the trigger member in a neutral position, obliquely-angled leaf spring members I92, I94 each have one arm lying upon and screwed to the face of the frame I80, while the other arm extends obliquely upward to engage converging adjacent faces of the trigger member I 88. On the opposite side of the trigger member from said converging faces semispherical buttons or nubs I88 are located near the ends of the trigger in position to be engaged by the ends of the one or the other of the bimetallic members. Thus, when either of the bimetallic members bend and press against either of the nubs or heads I 88, the trigger member I88 will be caused to pivot. In the central portion of the trigger member is molded a balanced tripping member which is balanced by having similar fingers such as I98 extending in opposite directions. The finger I88 extends radially of the pivotal axis beyond the surface of the tripping member in position to be engaged by the radial shoulder on a dynamically balanced rotary latch disc 200 which is driven onto, keyed to, or otherwise secured to, a stud shaft 202. To afford support for bearings for the stud shaft 202, the frame I80 has its extension I84 turned up at right angles to the central section of the frame I80 and its end I85 again turned at right angles so as to lie parallel to the central section I80. Conical bearing holes are formed in the end of the stud shaft 202 to receive the conical bearing member 204 located in the central portion of the frame I80 and to receive the conical end of a journal pin 208 which is screw-threaded into an aperture in the arm I85 co-axial with the conical bearing member 204. The pin 206 may be adjusted to remove all excess play and prevent movement under impact.

In order to bias the latch disc 200 in one direction normally, a coil spring 208 is placed around the end of the stud shaft 202 with one end of the spring 208 anchored in the frame I80, and the other anchored in the latch disc. In order to 1 limit the rotation of the latch disc, an arcuate recess 200a is formed adjacent the periphery thereof and extending through an angle of approximately 60 degrees. A pin I80a affixed in the central portion of the frame I80 extends up into the aperture 200a and acts as a stop to limit the rotation of the latch disc 200.

Carried by the stud shaft 202 at its end, is a movable self-aligning contact member made up of a pair of insulating discs 2I0, between which and to which are riveted a pair of bridging contact members 2 I 2 having the form illustrated in Fig. 9, namely a ring-shaped portion with diametrically opposite apertures for the rivets and with contact blades diametrically opposite each other but spaced degrees from the rivet holes. An insulating spacer disc 2I4 is placed between the two bridging contact members, so that the blades of the members may engage opposite sides of fixed contact fingers 2I8a (see Figs. 1 and 5). These fingers 2I6a extend radially inward as extensions from contact and terminal members 2H5 that may conveniently be stamped from highly conductive sheet metal into the oblique form shown in Fig. l. The members 2l-8 are bolted to the mounting disc I 30 in symmetrical positions of the axis of symmetry on opposite sides. Recesses having the same form and shape as the members 2I6 are provided for embedding said members in the base of the mounting disc I30. The outer ends of the members 2I6 are bent to provide terminal lugs, which are provided with terminal screws in conventional fashion.

In order to reset the thermal-overload opened contacts 2|: into position to bridge the contacts 2I6a, there is provided aresetting button in the form of a depressible insulating bar I80 sliding in a rectilinear tangential passage I82 in the disc I30. A spring I64 in the bottom of passage I82 urges the button outwardly of the passage; and a laterally extending arm I88 near the inner end 5'" er 'tfhebuddi positioned to engage man; I6 8- erg-tending from the surface ofthe latch 200-.- when the button is depressed, messengement rarm and pin causes rotation of the latch disc Z OIJ-aga'instthe urge orsprm 2 08 until'the finger; It} falls back} of the shoulderon; the'latcl disc to hold disc latched. in that position theg contacts 2l2 -and H6 are engaged. I: om the foregoing description of the" parts, it may be observed that Whenei ther one ortheother of the heater coils becomes overheated exc ss current, it will cause-sneer the other of the fiinietallic members to bend, so'that as'ena" gagesand turns the trigger member 188, cans 'tonguelorj extension [Q8 to disc shoulderon' the latch discZiH! (th-pos 1o springs i911 and I94 for maintaining the late mg member I88 in neutral position are not of lifntstrength to interfere with the over oad j seen r thefbimetallic mem er), As'soon'ss' t e latch disc 2001s free, the'spr'mgzcs will cause" td'idfiate'. Sincethestud shaft wltursn'swithi the latch d c, the movable contact structure will also hit and the bridging contact memberilz thereof win thereupon disengage the fixed members tobrak th control circuit. m convent" rial practice, the masses cdritrolled'by tfii's' tn rig mechanism will be in the holding nit of the elctromalgnet and their dis'eng will eau'se'the energizanon of the elect dmagnet coil, whereupon under the influence of tlfhiasingspring" the electromagnet contacts" and the shaft on which they are" mounted will r d'tat' into been circuit position, causing the switch to di n- .l

[Referring to Figs. 8 and 9, it will be observed that the pivots I99 Of the trig gel" I88 are" widely spaced; being approiiirnately the same is from the axis of the triggern'ieniber 188. thisvvide spacing of th'e'pivots, the friction by the; pivots 190 is less than it woul'd'beif these fiin's" wereinore c'llis'ely spaced and preview a shorter force arm, i. e. distance from thefingr I98 merrier pin l 90. Thus the friction created by the biasing effort of spring 268 is held down to practical elements.

The dynamic balance of movable parts is carried out in the overload devices by the structure of the trigger I88 with its oppositely-extending mutually balancing fingers I98" and the springs I92, use: which balance it in latching position, andimthe'balanced rotary contact structure' zifl, 212, 214 in which, also, the stationary contacts areengaged on both sides so as to p-revent'momentary disengagement due to shock occurring in axial direction.

Many modifications within the-scope of themvention will occur to thoseskill'ed inthe art. Therefore I do not limit the invention to' the embodiment disclosed.

I claim:

l. Overload relay mechanism for electric switches comprising an insulating disc centrally recessed for reception of control contact mechanism, rotary switch mechanism biased toward open-circuit position and embodying latching means for holding said switch mechanism in closed-circuit position, said switch mechanism and latching means being mounted on one side of said disc, plural overload responsive means mounted on the opposite side of said disc and engageable with said latching means to trip the same on occurrence of overload conditions aiiectdisc for esttmg said" switch mechahlsni'. V

2; ovr1dad relay mechanism 'ror' electric 5 switches as claimed in claim lwherein said switch mechanismis mounted and may be dismounted mechanism for" electric I -an' ins'ulatni'g' disc central-1y recessed for reception of ontrol contact mechanism rotary switch mechanism mounted onone i disc and biased toward open-circuit l p't'isitionand enibodying late i'n'g means for hold 0 mesa fnecli'aflis'Iii iii-closed-circuit positi'o plu er'load'responsive means mounted an the dpposit side of said disc and engagem ans to trip the same on n cenditions afiecting any of means-*and -manuarreset:

tside the disc for resetarid held -slid'ably eway' i'r'i' sjaid dis liysam switch unit. Over cad relay; mechanism for electric siw tc'hes comprising ai'frair'n having s aced par'-' a b a V overload reitor said trigger holdth s'ai'd' trigger member p ""e 1 -on said-lat'ch memdepddently' of "said ovenoad member. 7. Overload relay mechanism for electric switches comprising a frame, a rotary contact, a shaft carrying said contact and mounted between parallel portions of said frame, a latch member biased to open-circuit position, a trigger member pivotally mounted on said frame and holding said latch member, means holding said 70 trigger member resiliently in latching position, plural overload responsive devices engageable with said trigger member to release said rotary contact, said trigger member exerting its holding action on said latch member independently of said 75 overload responsive devices.

8. A balanced shockproo'f relay switch, comprising a stamped sheet metal frame, a shaft pivotally mounted in said frame, a balanced rotary contact on said shaft, fixed contact means engaged thereby, thermally responsive means to control said rotary contact, biasing means on said shaft for said rotary contact, and balanced latching means mounted on said frame holding said rotary contact against said bias and operated by said thermal means, all said parts except said fixed contacts and said thermal means being supported from said frame to provide an integra unit.

9. A balanced shockproof relay switch, comprising a stamped sheet metal frame, a shaft pivotally mounted in said frame, a balanced rotary contact on said shaft, fixed contact means having interleaved engagement with said rotary contact to prevent momentary separation of said contacts in case of sudden lateral impact, thermallyresponsive means to control said rotary contact, biasing means for said rotary contact, balanced latching means including a balanced trigger member normally holding said latching means and rotary contact and operable by said thermal means to release said contact, all said parts except said fixed contacts and said thermal means being supported from said frame to provide an integral unit.

10. A balanced relay switch comprising a balanced movable contact, fixed contact means engaged thereby, means biasing said movable contact, latching means holding said movable contact against said bias, and rotary trigger means engaged by said latching means and balanced about its pivotal axis in shockproof condition, plural spring means acting on said trigger in opposite directions to bias it in a central position while mantaining its condition of balance.

11. A balanced relay switch, fixed and movable contact means, rotary latching means for holding said movable contact means, biasing means for said latching means, pivoted trigger means engaging said latching means and movable at right angles to the plane of movement of said latching means to minimize transmission of forces, the pivots of said trigger means being separated to reduce frictional resistance in its pivotal mounting incident to the force which the biasing and latching means exert on said trigger means.

12, A balanced shockproof overload relay comprising a recessed insulating disc having on one side a rotary switch unit and on the other side plural overload responsive and thermal means,

sive means comprising separate cantilever type bimetals acting on said trigger means, said thermal means being connectible to power lines to effect said overload responsive means, said overload and thermal means being separately assembled in one recess of said disc, stationary contact means mountable in and engageable by said rotary contact in latched position, reset means mountable on disc engageable with, but nevertheless movable independently of, said latch to cause re-engagement of the latch and trigger.

13. A balanced shockproof overload relay comprising a centrally recessed insulating disc having on one side a rotary switch unit and on the other side a plural overload responsive means, said rotary switch unit comprising a frame, a pivotally mounted rotary balanced contact and latch assembly, biasing means for said contact and latch assembly, balanced trigger means pivotally mounted upon said frame and engageable with said latch assembly resilient means to statically balance said trigger means in latching position, said overload responsive means comprising separate cantilever type bimetals, fixed contact means engaged by said rotary contact, and reset means mountable on said disc and engageable with said latch to re-engage it with the trigger.

14. A balanced shockproof overload relay comprising a recessed insulating disc having on one side a rotary switch unit and on the other side plural overload responsive means, said rotary switch unit comprising a frame, a pivotally mounted rotary balanced contact, a latch, biasing means for said contact and latch, a balanced trigger pivotally mounted upon said frame and engageable with said latch, resilient means to statically balance said trigger in latched position, said overload responsive means comprising separate cantilever type bimetals acting on said trigger means, stationary contact means mountable in said disc and engageable by said rotary contact in latched position, reset means mountable on said disc and engageable with, but nevertheless movable independently of said latch to cause re-engagement of the latch and trigger.

HAROLD E. SCI-ILEICHER.

REFERENCES CITED The following references are of record in the file of this patent:

said rotary switch unit comprising a frame, a

pivotally mounted rotary balanced contact, a latch, biasing means for said contact and latch, a balanced trigger means pivotally mounted upon said frame and engageable with said latch, re-

silient means to statically balance said trigger means in latched position, said overload respon- UNITED STATES PATENTS Number Name Date 652,601 Dodds June 26, 1900 1,328,481 Baker Jan. 20, 1920 1,701,440 Chatto Feb. 5, 1929 1,736,372 Sachs Nov. 19, 1929 1,740,911 Todd Dec. 24, 1929 2,067,797 Smith Jan. 12, 1937 2,089,716 Smith Aug. 10, 1937 2,416,163 Dyer Feb. 18, 1947 

